Combustion-powered tools are of course well-known. A preferred system for combustion-powered tools comprises the use of a first or primary combustion chamber, and a second or secondary combustion chamber, wherein the first and second combustion chambers are separated from each other by means of a wall, however, they are also fluidically connected to each other by means of a control check valve. In this manner, the control check valve effectively permits unburned fuel and the flame front, generated within the first or primary combustion chamber as a result of the ignition of the air/fuel mixture disposed within the first or primary combustion chamber, to travel across the control check valve, enter the second or secondary combustion chamber, ignite the air/fuel mixture disposed within the second or secondary combustion chamber, and yet effectively prevent the combustion products generated within the second or secondary combustion chamber from flowing back into the first or primary combustion chamber as a result of the closure of the control check valve back to its original closed and seated position prior to the ignition of the air/fuel mixture within the first or primary combustion chamber. The combustion of the air/fuel mixture within the second or secondary combustion chamber is therefore effectively wholly contained within or confined to the second or secondary combustion chamber whereby the pressures developed within the second or secondary combustion chamber, as a result of the ignition of the air/fuel mixture within the second or secondary combustion chamber, can act upon the working piston so as to drive the same through its working or power stroke.
It is also noted that the use of two, serially connected combustion chambers, that is, a first or primary combustion chamber and a second or secondary combustion chamber, as has been briefly described hereinbefore, results in the development of pressure levels to power or drive the working piston which are greater and more efficient than those that would normally be capable of being achieved by means of a single combustion chamber. It is necessary, however, that, in order to achieve these greater pressure and efficiency levels, the control check valve must be capable of meeting several operational parameters. For example, the control check valve must be capable of withstanding high mechanical shocks, such as, for example, when the rapid explosive combustion takes place within the second or secondary combustion chamber. The control check valve must likewise be capable of operating under minimal pressures being exerted upon the side of the control check valve that is exposed to the first or primary combustion chamber, as a result of the combustion of the air/fuel mixture within the first or primary combustion chamber, so as to be quickly unseated from its valve seat and thereby permit a relatively high flow rate of unburned fuel and resulting flame fronts to pass by the control check valve from the first or primary combustion chamber and into the second or secondary combustion chamber in order to initiate combustion of the air/fuel mixture disposed within the second or secondary combustion chamber, and it must be capable of doing this without causing any quenching of the flame fronts. Still further, the control check must be capable of quickly returning to its original closed and seated position so as to contain or confine the air/fuel mixture within the second or secondary combustion chamber, and to effectively and repeatedly provide a perfect seal with its valve seat. Lastly, the mounting of the control check valve upon its valve seat and within the system must be considered so as to in fact permit the aforenoted operational parameters to be achieved.
Different types of valves have been previously attempted to be used within such combustion-powered tools, however, they all resulted in failure for one reason or another. For example, metallic reed valves were tried, however, they were difficult to mount at their operational positions, and they were prone to structural failure due to their incapability of withstanding the shock loading characteristic of the rapid explosive combustion taking place within the second or secondary combustion chamber. Accordingly, the valves were effectively deformed so as not to be capable of returning to their original positions and resuming their sealing functions. They were also unable to quickly react to the initial pressures developed within the first or primary combustion chamber such that the desired flow rates of the combustion products and the propagation of the flame fronts from the first or primary combustion chamber, into the second or secondary combustion chamber, could be achieved. Additional reed valve designs comprised the use of smaller multiple ports in lieu of a relatively large single port, however, this also resulted in operational failure due to the fact that the flame front was extinguished or quenched as the flame front passed through the multiple ports.
Poppet valves have also been experimented with, however, in view of the fact that the control check valve needs to act extremely quickly, that is, the control check valve needs to return to its original closed or seated position within a time frame of between 1-2 milliseconds, the poppet valve needed to be provided with a biasing spring which would exhibit substantial tension. Unfortunately, in view of this, the poppet-type control check valve exhibited low fluid flow rates, flame quenching, and other operational problems which rendered the same unusable for use in such combustion-powered tool systems.
A need therefore exists for a new and improved combustion-powered tool, comprising a first or primary combustion chamber and a second or secondary combustion chamber, wherein a control check valve can be operatively interposed between the first or primary combustion chamber and the second or secondary combustion chamber, and wherein the control check valve can in fact withstand the high mechanical shock pressures and forces attendant explosive combustion conditions present within the second or secondary combustion chamber, the control check valve can withstand the high temperature levels present within the combustion chambers, the control check valve will not suffer a breakdown in its structural integrity so as not to, in turn, become deformed whereby the control check valve would no longer be capable of achieving its sealing functions, and the surfaces of the control check valve will also be characterized by excellent wear characteristics as well as low temperature absorption properties so as to eliminate quenching.